This invention relates to the area of pneumatic transportation of particulate or granular material. It has become common to design bulk material handling systems for handling particulate or granular materials by using compressed or pressurized air or gas to move the material through pipes. This technology is based upon the fact that such materials when exposed to a gas at an elevated pressure become aerated up by the gas which penetrates throughout the material and converts it from a solid to a fluid mass having many of the characteristics of a liquid. This process is referred to as fluidizing the material and permits it to be transported for a distance through pipes as though the material were a liquid.
It is of course well known, that as the pressure drops within the material, the individual particles settle out and the material falls out of the stream of gas forming piles. This is much the same phenomenon as results in sand dunes in a desert; it limits the distance to which the material can be moved and also puts outer limits on the speed and mass of material that can be moved with a given unit of air.
This technology has led to the development of various pressurization systems within the field of pneumatic material handling. One of the essentials for fluidizing the material to be handled is that it be pressurized; that is, it is exposed to a gas at a pressure well above normal atmospheric pressure. As a result, the existing state of the art requires that the material to be handled be moved into a pressure vessel which is then sealed and pressurized to provide the essential fluidization.
These pressure vessels thus result in all current pneumatic material handling systems being essentially non-continuous flow. A batch of material must be accumulated and then in turn transported into an enclosed pressure vessel. No further material can be put into the pressure vessel until all material within the pressure vessel has been transported. The pressure vessel may then be refilled. This results in a requirement for at least two holding units, including the pressure vessel, and an interruption in the flow of the material. It severely complicates the construction of material handling facilities, most of which are fed by continuous flow means.
It also makes pneumatic handling systems unsuitable for certain flow critical material handling systems. One such is in cement plants. Continuous flow of the cement is essential, as kiln startup and shutdown for batch flow is infeasible due to the thermal load imposed by startup and shutdown. As a result, alternate, less efficient material flow systems are used, largely based on pressure-tight screw-feed mechanisms.
In addition, within a given pneumatic system the physical design of the system determines its range, the distance to which the material can be transported. Previous attempts to overcome range restrictions have been in the form of introducing, at periodic intervals along the transportation pipe, points at which additional compressed air can be introduced into the flow of material. However, even with this improvement, it has remained that for a given physical design the distance to which the material being handled can be transported is essentially a constant, fixed by the design of the system and not variable by its subsequent operational conditions.
The above restriction is largely due to the fact that the fluidization of the material is a function of the initial feed pressure vessel design. This feed pressure vessel is of such a large size, in order to achieve a reasonable material movement rate, that it essentially determines the volume and pressure of the pneumatic gas feeds to be provided to the overall system and thus controls the characteristics of the pneumatic material transportation system.